This invention relates to electrical stimulation apparatus and methods for use in stimulating body organs, and more particularly to implantable apparatus for stimulating neuromuscular tissue of the viscera of the organ structure, including the gastrointestinal tract and methods for installing the apparatus in a patient.
The field of electrical tissue stimulation has recently been expanded to include devices which electrically stimulate the stomach or intestinal tract with electrodes implanted in the tissue. These gastric stimulators have been found to successfully combat obesity in certain studies. Medical understanding as to how this treatment functions to reduce obesity is currently incomplete. However, patients successfully treated report achieving normal cycles of hunger and satiation.
An apparatus and treatment method for implementing this therapy was described in U.S. Pat. No. 5,423,872 to Dr. Valerio Cigaina, which is hereby incorporated by reference in its entirety herein. The apparatus described in the Cigaina patent stimulates the stomach antrum pyloricum with trains of stimulating pulses during an interval of about two seconds followed by an xe2x80x9coffxe2x80x9d interval of about three seconds.
U.S. Pat. No. 5,836,994 to Bourgeois describes a laparoscopic device which has a needle which passes through the tissue being stimulated, and a thread attached at one end to the needle and at the other end to an implantable pulse generator (IPG) lead. The entire device can be inserted into the body via a laparoscopic type tube, or trocar, as it is relatively long and narrow. Many devices are known to be inserted through a trocar by having a needle attached with a thread to the devices.
Cigaina U.S. application Ser. No. PCT/US98/1042 filed on May 21, 1998, and Cigaina U.S. application Ser. No. 09/122,832, filed Jul. 27, 1998, now U.S. Pat. No. 6,041,258 both of which are incorporated by reference in their entirety herein, describe a novel apparatus wherein the needle is incorporated into the end of the lead. Once the electrodes are inserted into the viscera, the electrodes are fixed in place by partially opposing tines.
The above apparatus and methods of installation generally incorporate a pair of electrodes for stimulating the tissue. As illustrated in FIG. 1, a first electrode 1 and a second electrode 2 are implanted in the patient""s tissue 3. When electrical stimulation is applied to the tissue 3, a pulsed electric field 4 propagates outward from the electrodes 1 and 2 in a direction 5 generally perpendicular to the direction 6 of electrode axis, typical of a directional dipole.
Under certain circumstances, it may be necessary to provide electrical pulses that stimulate a greater area of tissue in order to obtain the desired tissue response and entrainment. For example, certain patients may benefit from stimulation over a larger area of tissue. Thus, there is a need to provide an electrode apparatus that stimulates tissue over a greater area in a more uniform or omnidirectional fashion.
Moreover, variations in the stimulation location, direction, duration, and intensity over time may be beneficial. It is an advantage of the invention to provide an apparatus and methods of stimulation wherein the stimulation patterns may be varied over time.
It is also an advantage of the invention to provide an apparatus and methods of stimulation wherein the electrodes may be implanted in a minimally invasive manner, such as laparoscopically, which allows substantially equidistant spacing of the electrodes.
These and other objects of the invention are accomplished in accordance with the principles of the invention by providing apparatus and methods for attaching such apparatus to neuromuscular tissue of the viscera, and particularly, the gastrointestinal tract. The apparatus includes at least four closely spaced stimulating electrodes electrically connected to a pulse generator that supplies electrical stimulating pulses to the neuromuscular tissue. According to a preferred embodiment, an electrode assembly includes a first electrode-pair attachment member supporting a first pair of electrodes and a second electrode-pair attachment member supporting a second pair of electrodes. Each electrode-pair attachment member includes first and second anchor members that secure the electrode attachment member and the electrodes in the tissue. Such anchor members may be a set of resilient tines which abut the tissue and prevent relative movement with respect thereto.
In the most preferred embodiment, the electrode assembly has a pair of electrode-pair attachment members arranged in parallel, each having a respective penetrative mechanism and a severable connecting member for removably attaching the penetration mechanism to the electrode attachment member. The first electrode-pair attachment member pierces the tissue with the first penetrative mechanism and anchors itself at a first location. The second electrode-pair attachment member pierces the tissue with the second penetrative mechanism and anchors itself at a second location, and in a position substantially parallel to the first electrode-pair attachment member.
In another preferred embodiment, the electrode assembly has the two electrode-pair attachment members arranged in series. One penetration mechanism is provided and connected to the one of the first and second electrode-pair attachment members, and a bridging portion connects the first and second electrode-pair attachment members. The penetration member allows the first electrode-pair attachment member to enter at a first location, pass through, and exit the tissue at a second location, and subsequently guides the second electrode-pair attachment member to enter and be anchored at least partially within the tissue at the first location. The first electrode-pair attachment member subsequently enters at a third location and anchors itself within the tissue, and in a position substantially parallel to the second electrode-pair attachment member. The parallel installation of the first and second attachment members allows the four electrodes to be substantially equidistant with respect to each other.
In yet another preferred embodiment, an electrode attachment member is provided to install four electrodes at the surface of the neuromuscular tissue. The electrode attachment member supports the four electrodes at a distal surface thereof and is configured for attachment to the surface of the neuromuscular tissue to provide an electrical interface between the electrodes and the neuromuscular tissue. The electrode attachment member preferably has a substantially flat distal surface fabricated from a flexible material. This flexibility allows the distal surface to substantially conform to any curvature of the neuromuscular surface. The flexibility also permits the electrode attachment member to be reduced in size to a compact form by rolling, folding, etc. The electrode attachment member may be inserted into the patient while in the compact form through minimally invasive laparoscopic or similar surgical access openings. A cylindrical sleeve member or annular bands may be provided to surround the electrode attachment member to assist in maintaining it in the compact form.
Preferred methods for installation in accordance with the invention include providing an electrode assembly which supports the four electrodes. A further step may include providing a surgical access opening in the patient and laparoscopically introducing the electrode assembly into the patient. A subsequent step may include attaching the electrode assembly to the neuromuscular tissue to provide an electrical interface between the electrode and the tissue.
Once the electrode assembly has been installed, thereby orienting the four electrodes to the tissue, it is possible to begin stimulating the tissue in a novel manner. In a preferred embodiment, a normal generator is provided to generate the stimulating pulses, and a switching matrix is provided under firmware control to control a sequential pair-wise stimulation sequence.
The pair-wise stimulation sequences may include a plurality of options. A first stimulation technique may be a quadrapole sequence, wherein electrode pairs at diagonally opposite corners apply a pulse of the same polarity, and adjacent electrodes apply pulses of opposite polarity. A second stimulation technique may be a sequential quadrature bipole, wherein stimulation pairs consist of electrodes at opposite corners that may sequentially stimulate the tissue. A third stimulation technique may be a sequential quadrature bipole, wherein stimulation pairs consist of adjacent electrode pairs that may sequentially stimulate the tissue.
In a preferred embodiment, the pulse parameters may include the timing and duration of pulses applied according to one of the above sequences. In order to vary these parameters during the treatment period, the neuromuscular stimulator may also include a real time clock and a programmable calendar for tailoring the stimulating waveform parameters over the treatment period. The real time clock supplies data corresponding to the time of day during the treatment period. The programmable calendar stores parameters which refer to the shape of the stimulating waveform. Each of the parameters may be referenced directly or indirectly to the time of day. Circuitry, such as a control circuit, applies the stimulating pulses which are defined by the parameters at the appropriate times of the day during the treatment period.
The real time clock and the programmable calendar allow the stimulating waveform to vary over greater periods of time. For example, the real time clock may supply data corresponding to a week during the time period. Consequently, the waveform may be programmed to apply a different waveform during each particular week in the treatment period. The real time clock may also supply data corresponding to the day of the week during the treatment period. Alternatively, the real time clock may supply data corresponding to a month of the year during the treatment period, such that the waveform may vary from month-to-month as the treatment progresses. Moreover, the real time clock may also supply data corresponding to the day of the month, and/or the day of the year.
Although electrode assemblies are illustrated in the form a pair of elongated bodies or of a patch, certain aspects of the invention are equally applicable to electrode assemblies having other shapes and other methods of installation, as well as alternative four pole stimulation sequences.